Derrick Jones Jr. said the last time anyone measured his vertical leap was his senior year at Philadelphia’s Archbishop John Carroll High School.

“It was 48 [inches] at the time,” the 20-year-old, 6-7, 200-pound second-year swingman out of UNLV said about an hour before making his first start of the season for the Miami Heat Jan. 10 in Indiana. “I’ve gained weight. I don’t know what it is right now. I know it’s still pretty high.”

“On a good day,” Jones Jr. said he can slap his hands on the top of the backboard.

“On a great day,” he continued, “I can probably jump [and put my hands] over the backboard.”

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Jones’ freakish leaping ability is what got him to the NBA. His heart and hustle – coupled with those hops – is what continues to impress his teammates and his coaches, and it’s why Jones Jr. could very well remain with the Heat when his two-way contract expires (he’s got nine NBA-eligible days left after Monday before the Heat would have to open up a spot on the 15-man roster to keep him).

The Heat, which has dealt with a rash of injuries all season at guard, knows Jones Jr. has a ways to go when it comes to his shooting (he’s 4 of 16 on jump shots including 1 of 10 beyond nine feet). But defensive plays like the one he made in the first half of Saturday’s win in Charlotte – when he ran down Kemba Walker for a block that was ultimately ruled goaltending – is why coach Erik Spoelstra loves his potential.

“That’s indicative of what we’re talking about, competing every single possession like it’s the most important possession, regardless of the score, regardless of the circumstance,” Spoelstra said Monday at shootaround in Houston. “He had no chance to get that block, but he ran 80 feet to catch Kemba Walker and ended up getting a goaltend on it. But I think there’s a karma to that.”

Sunday in Houston, Jones Jr. put on a dunk display for his teammates, who were happy to film some of those slams and share them on social media. A finalist in last year’s dunk contest as an undrafted rookie in Phoenix, Jones, nicknamed Airplane Mode, has six dunks thus far in seven games with the Heat. He’s also got 10 blocks – with several of the chase-down, highlight-reel variety.

Since Tyler Johnson went down with a left ankle injury at Chicago on Jan. 15, Jones Jr. has started three consecutive games and averaged close to 20 minutes a game, producing 2.7 points, 2.7 rebounds and a block per game while shooting just 22.2 percent from the field. But it’s not about getting a big contribution from Jones Jr. on the offensive, Spoelstra said. It’s more about big moments and big plays.

“We like the minutes that he’s been giving us,” Spoelstra said last week. “It’s more about developing the right habits and approach and behavior, about developing his future. Like we say all the time with our young guys, including Bam, that future is now. So we also expect you to be able to produce when you get out there. He doesn’t have to play outside his role. He doesn’t have to do anything bigger than expected. He just has to bring a lot of energy, athleticism, attention to detail defensively and that’s enough for us right now.”

Jones Jr., meanwhile, feels like he can learn a lot from his time with the Heat. He takes pride in his defense and feels like he can take it up to another level with the way Spoelstra and his coaching staff emphasize it.

“I was very excited to come here because at the end of the day it’s a bunch of hard workers in this locker room and a bunch of hard workers that came from this organization,” he said. “And I feel like that’s something that I want to be. I want to be one of those hard-nosed players that go out there and my teammates can rely on me to do whatever they need me to do.”

The baseline angle of @therea1djones taking off day flight in Houston ✈️

For now, his teammates enjoy whatever he can provide – including some amazing dunks in practice.

“He flies, man,” Wayne Ellington said Monday at shootaround. “He gets so much lift and he’s so creative when he’s in the air, it’s unbelievable. The athleticism is unlimited.

“It would be great to see him get another chance at [the dunk contest]. I think he’ll win it. He missed a dunk [last year]. We were actually talking about it, he said he missed a dunk. He was so mad at himself because all he had to do was make the dunk and he felt like he would have won. He’s a guy that can be in the dunk contest every year and have a chance to win.”

What’s the best dunk Jones Jr. has done in practice?

“He’s done so many already,” Ellington said before being asked if the between the legs baseline dunk Jones Jr. did Sunday in practice was his most impressive.

“That wasn’t even the best one,” Ellington replied. “I’ve seen him throw it off the glass, jump from the free-throw line and damn near catch it from back there. It’s like he’s Stretch Armstrong or something. Off of two feet, by the way.”